Automatic telephone system



r. G. MARTIN AUTOMATIC TELEPHONE sysmu Filed Feb. 14. 1921 2 Sheets-Sheet 1 T2151" ENE rim mum May 4 1926. r

T. G. MARTIN AUTOMATIC TELEPHONE SYSTEM Filed Feb. 14. 1921 2 Sheets-Sheet 2 ----Inu5n [Jr- TEZEET El 'arzn Patented May t; 1926.

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TALBOT G. IlVIAR/lIN, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO

AUTOMATIC nLEo'rnrc INC., on carcass,

WARE.

AUTOMATIC TELEPHONE Application filed February 14, 1921. Serial No. 444,663.

and a resident of Chicago, Cook County, and

State of Illinois, have invented certain new and useful Improvements in Automatic Telephone Systems of which the following is specification. V r

The present invention relates in general to automatic telephone systems, and is adapted to be usedin a system of the multiofiice type. More specifically, the invention is adapted tobe used in an automatic ofiice wherein there are a number of trunks extending to another automatic exchange. In such a sys tem, in order to provide a large number of trunks extending to the second automatic exchange from one level ofselector switches, outgoing secondary line switches are used. If self aligning plunger typeline switches are used'in such a case, a certain difficulty manifests itself which is that the line switch may, under certain conditions, be plunged in on a busy trunk line. Self aligning line switches are so constructed that immediately upon the release of-theplunger arm after being 0perated,it assumes a position before the trunk line preselected by the associated imaster switch; In this arrangement there is a short interval when the line switch is assuming this position during which if seized immediately it may plunge in on a busy trunk line.- Anobject of the present inven tion, therefore, is to provide means for positively preventing the seizing of such a switch until it has assumed its position in front of the preselected trunk line.

Another object of the invention is to provide means for rendering the trunk lines in the selector level busy in case all the outgoing trunk lines in a' group are in use.

7 The particular manner in which these and other results are accomplished will be described hereinafter reference being had to the accompanying drawings in which Figs. 1 and 2 show by means of the usual circuit diagrams sufficient of the apparatus in an automatic telephone system to enable the in vention to be explained and understood, while Fig. 3 shows the mechanism of a selfaligning plunger.

Referring now to the drawings, in Fig. 1 is shown the usual automatictype of substation A having an individual line switch C of the well known plunger type llidiVl(lliiil thereto; Theline switch C in common with a plurality of other line switches is' adapted to be controlled by a master switch D; The function of the master switch D as is well known is to maintain the plungers of all idle line switches opposite an idle trunk line. The trunk lines accessibleto the line switch C and other similar line switches terminate in selector switches one of which is shown at E. The selector E is of the usual Strowger vertical and rotary type having the usual set of 100, bank contacts arranged? in ten rows ,or levels. Some levels of these selector switches lead to second. selectors which in turn-have access to connector switches. In other levels of bank contacts are terminated trunk lines which extend to outgoingysecondary line switches. The bank contacts 8587,' inclusive, accessible to the selector Eterminate in the outgoing secondary line switch C, Fig. 2. v

The mechanical construction of the plunger arm of the line switch C1whereby the self aligning feature is .secured isshown in Fig. 8. It will be seen that in place; of the usual-slot in the fan of the plunger arm two arms 255 and 2 are used which are pressed into engagement with the guide on the master switch shaft 257 by the" spring 258. When the line switch is operated the plunger arm guides 255- and 255 do not. disengage the guide 256 on the master switch shaft. As the master switch operates seeking an idle trunk line the arm 255 is forced, out of its normal position by the guide on the master switch shaft. WVhenlthe lineswitch is released the spring 258' causestheplunger arm to assume a position in front ofthe trunk line preselected by the master switch. Line switches of this'type are well known and their operation will be readily understood from the above description.

At G is shown, themaster switch which is associated with the line switch C and a plurality of other outgoing line switches, whose function is to maintain the plungers .of the line switches in front of an idle trunk access. lead to repeaters one of which ILLINOIS, A COBEORATIOIN OF DELA- l shown at F. The repeater F is of the usual automatic type and constitutes the terminal of a trunk line extending to another automatic exchange.

Having briefly described the apparatus involved in the invention a detailed description of its operation will now be given. For this purpose it will be assumed that the subscriber at substation A desires to call a subscriber in another automatic exchange.

When the receiver is removed at substation A a circuit is completed for the line relay 20 over the line conductors 11 and 12 in series. Upon energizing, the line relay 20 at its armature. 32 completes the circuit of the pull down winding 25. The pull down winding upon energizing, attracts the plung er arm 28 thereby forcing the springs 40 p 13, inclusive, into engagement with their working contacts. The cut off armature 29 s also attracted by the energization of the pull down winding By the engagement of springs 40 and 43 with their working contacts the line conductors 11 and 12 are extended. by way of armatures 70 and 73 and their back contacts to the upper and lower windings of the line relay of the selector E.

The line relay 50 is energized over the line circuit of the calling subscriber and closes at its armature the circuit of the slow acting release relay 51. The latter relay upon operating, at armature 62 prepares the operating circuits of the selector E and at armature 61 places ground on the release trunk conductor 63 thereby establishing a holding circuit which extends by way or working contact of spring 41 and the said spring, and through the holding winding of the line switch 0 to battery. The energization of the holding winding 26 serves to maintain the cut oil armature 29 and the plunger arm 28 in an operated position. it will be noted that the cut 0E armature upon operating opens the circuit or the line relay 20, and it will be understood that the circuit for the holding winding 26 was completed before the line relay 20 had time to deenergize. A branch of the holding circuit extends by way of the private normal conductor 89 to multiply connected test contacts in the banks of connector switches which have access to the line of the substation A whereby the said line is protected from intrusion in the well known manner.

By the engagement of spring 42 with its working contact ground is placed on thecircuit of the line relay 50 which deenerglzes a corresponding number of times. At each retraction of its armature 60 an impulse of current is sent over the following circuit: Ground byway of back contact and armature 72, armature 60 and its back contact, armature 62 and its front contact, winding of the slow acting series relay 52, and thence through the winding of the ver-- tical magnet 55 to battery. Magnet 55 operates to raise the switch wipers 80S2, inelusive, step by step until they are placed opposite the level of bank contacts in which are terminated trunk lines leading, to the outgoing secondary line switches. The slow acting relay 52 which is energizcdin series with the vertical magnet maintains its armature attracted throughout the vertical movement of the switch. Upon the first vertical step of the switch shaft a circuit is completed extending from ground on release trunk conductor 63, by way of armature 64.- and its front contact, oft normal spring 65 and its working contact, winding of the intcrrupter relay 5 working cont-act or' spring 75 and the said spring, and back contact and armature 69 to battery. Upon energizing, relay 53 at arn'iature ()7 establishes a locking circuit for itseli and at armature 68 prepares the rotary magnet circuit. Upon the termination of the vertical morement of the switch the slow acting relay 52 is deenergized tending from ground on release trunk con ductor 63 by way of armature 64: and its back contact, armature 68 and its front contact, and through the winding of the rotary magnet- 56 to battery. The rotary magnet 56 operates to rotate the switch wipers into engagement with the terminals of the first trunk line in the selected level and at the same time breaks the locking circuit of the interrupte relay 53 at armature 69. Relay 53 then deenergizes opening the circuit of the rotary magnet 56 which deenergizes also. The operation of the selector E now depends upon whether or not the-trunk line with which the switch wipers 8082, inclusive, are in engagement is or is not busy. It busy. there will be a ground potential pres ent on the test contact engaged by test wiper 81 and circuit may be traced extending from the said grounded test contact by way of test wiper 81, armature 71 and its back contact, ofi' normal spring 65 and its working contact, through the winding of the terrupter relay working contact oi spring 75 and the said spring, and back contact and armature (39 to battery. The interrupter i'elay 53 is again energized over this circuit and operates in the same marineas before to establish a locking circuit for it r? at armature 67 and at armature 68 to complete the rotary magnet circuit. Magnet 56 operates to rotate the switch wipers into eng 119* and a circuit is completed e.\' V

.mcnt with the bank contacts associated with deenergizes. also, The-alternate operation of the interrupter relay 53 and the rotary magnety56 will continue until an ldle trunk is found, which we will assume is the trunk .line shown mthe drawlngs terminating inv bank contacts 8587, inclusive. WVhen this occurs there being no ground present on the test contact 86 engaged by-test wiper 81 the switching relay 54% will be no longer short circuited. A circuit may thenbe traced ex tending from ground on release trunk conductor 63, through the winding of the switching relay 5 1, off normal spring 65 and its working contact, through the winding of the interrupterrelay 53, working contact of spring and the said spring, and back contact and armature 69 to battery. It may be stated at this point that the switching relay 54 is of comparatively high resistance and relay 53 willnot operate over the above-circuit. V

The spring 7 5 is controlled by the double .dog of the switch and hence when the release magnet operates the spring 75 is shifted out of engagement with 1ts working contact. It w1ll thus be noted that the spr ng 7 5 remains in engagement with its working contact as; long as the swltch 1s 1112.11 operated position, but 15 immediately forced out of en-- gagement therewith by the operation of the release magnet.

Returning now to the operation of the selector E when the switching relay 5% is energized,- upon operating, this relay at armatures 7 0 and 7 3 disconnects the incoming line conductors from the windings'of the line relay and extends them by way of wipers and 82, bank contacts and 87,

to the trunk conductors and 92. -Upon operating, relay 54:. also extends ground by way of front contact and armature 71, test wiper 81, test contact 86, release trunk conductor 91, springs 109, armature 115 and its back contact, through the winding of the pull down winding 101 of the secondary line switch C, armature 215 and its back contact, armature 212 and its back contact, and thence through the winding of the slow acting-relay .191 to battery. The pull down winding 101 andthe slow acting relay 191 are energizedover this circuit, relay 191 completing at its armature 211 a circuit of the peg count meter. The pulldown winding 101, upon energizing, attractsthe plunger arm 105 and the cut off armature 106.-

The plunger arm 105-forces the springs 113, inclusive, into engagement with their Working contacts. By the engagement of springs 110 and 113 with their working contacts the incoming trunk conductors in series with a slow acting alarm.

:90 and,92 are extended by way/of normally closed springs controlled byarmatures and 162 through the upper and lower windings of the linerelay 1510f the re- I 'peater. F.

The line relay" 151 is energizedover the calling s'ubscribers line loop and closes at its armature 165, a circuit of the slowracting armature,169,.at,armature 171 completes a circuitof the polarizing winding of the polarized relay. 154, and at armature placesground on release trunk conductor 179 thereby establishing a holding circuit which extends byway of working contact of spring 111 and the said spring, working contact of spring-108 and the said spring, winding of the slow acting relay 190, and through" the holding winding of the line switch C to battery. The operation of relay 100, however, is without function at this time. The holding winding 102 upon energizing, maintains the cut off armature106 and the plunger arm 105 in their operated positions. A branch of this holding circuitalso extendsby way of therelease trunk conductor 91, bank contact 86, test wiper 81,

armature 71 and its front contact, where it divides one path extending back tothe holding-winding of the line switch C, the other pletes .a circuit extending from ground through thelow resistance \V1I1Cl111g.0f relay 192' by way of front contact and armature 216,1thro-ugh the winding of the locking magnet 19.6, and thence by way of back contact and armature 210 to battery. The locking magnet 196 energizes over this circuit and-at armature 225 and its front contact completes a circuit for the high resistance winding of relay 192. Relay 192 will be energized over this c rcuit andv at armature 213 will complete the circuit of the lamp L V This PIOVlSlOll'lS made so that should anything go wrong with the master switch the alarm 1 willcome in andthe exchange attendant may at once find the trouble. The locking magnet 196 also withdraws the locking pawl from the master switch segment thereby causing the master switch to rotate under influence of its spring in search of an idle trunk line. lVhenthe master switch wiper 235 engages the bank contact of an idle trunk line the starting. relay 193 is .deenergized and immediately opens the circuit of the til locking magnet 196 which allows the locking pawl to again engage the locking segment.

It will be noticed that a branclrot the holding circuit extends through the winding of the chain relay 200 to battery. Relay 200 upon operating, at armature 24:1 completes one point in the chain. Should all the trunks of a group happen to be busy all the chain relays similar to relays 200, 201 and 202 will be energized and a circuit will be completed for the stop relay 190. A branch of this circuit also extends to another meter which thus registers each time all trunks become busy. The relay 190 upon energizing, removes battery from the locking magnet 196, from the solenoid 227 and the trip relay 195 of the master switch G thus preventing the master switch from rotating under these conditions. As all trunks are busy there will be a ground present on the bank contact engaged by the master switch wiper 235 and the start relay 198 will be energized. Ground is thus placed by way of the pull down windings of the secondary line switches on the release trunk conductors extending back to the selector switches similar to E whereby the selectors are prevented from seizing these trunk lines. As soon as any one of the trunks become idle the associated chain relay is deenergized, and the circuit of the stop relay 190 is opened at this point. The relay 190 immediately deenergizes again extending battery to the master switch which operates to select the trunk which has become idle.

The calling subscriber may now operate his calling device for the next digit of the desired subscribers number. A series of interruptions are thereby produced in the circuit of the line relay 151 of the repeater F which retracts its armatures a corresponding number of times. At each retraction of its armature 1.65 an impulse of current is sent to the slow acting relay 153. When the line relay was first energized a bridge was placed across the trunk conductors 180 and 181. This bridge extends by way of armature 169 and its front contact, armature 175 and its back contact, upper winding of the polarized relay 154 normally closed springs ore-r this circuit and completes a circuitof each operation of the calling device at substation A a series of interruptions will be tend a connection-to the desired called subscriber. When the receiver is removed at the called substation the back bridge relay oi the connector switch used in the connection is operated and serves to reverse the polarity of the battery supplied to the trunk conductors 180 and 181. The polarized relay 154 in the repeater E immediately operates completing the circuit of the reversing relay 150 at armature 177 and completing the talking connection. Relay 150 operates to reverse the battery back to the calling subscribers line in order to operate a meter or for any desirable purpose and at armature 163 places both windings of the impedance coil 155 across the bridge of the trunk conductors thus materially improving the transmission. The calling and called subscribers may now converse with each other battery being supplied to the calling subscriber from the windings of the line relay 151 oi": the repeater F; and to the called subscriber from the windings of the back bridge relay in his associated connector switch.

When the conversation is terminated the calling subscriber at substation A by replacing his receiver upon the switchhook will cause the deenergization of the line relay 151 of the repeater E which immediately deenergizes breaking the circuit of the slow acting release relay 152'. The latter relay will deenergize after a short interval breaking the circuit of the line relay of the connector switch which is in the distant exchange and removing ground. from the release trunk conductor 179. When ground is removed from the release trunk conductor 179 the associated chain relay 200 is deenergized as is the holding winding 102 ot the outgoing secondary line switch C and the switching relay 5 1- of the selector E and the holding winding of the individual line switch C. Upon the denergization of the holding winding of the line switch G the plunger arm and the cut oil armature immediately assun'ic their normal positions.

llhcn the switching relay 5% deenergizes the circuit of the release magnet 57 is completed and the switch is restored to its normal position.

with the release of the seictorswitch.

By the operation of the re lease magnet 57 the spring is opened.

The holding winding 1O2 of the line switch C, upon (lEQDQIglZlllg, allows the cutoff armature 106 and theplunger arm' 105 to immediately restore to normal-position. The circuit of the slow-acting relay 1001s broken as soon as-grou-nd1s removed fromthe release-trunk conducto-r'9l butas I this relay-is slow acting it will not immediately retract its armature-. Ground" is thus again placed on therelease trunkycon= ductor 91 as soon as the-cut oli armature 106 of the line. switch C" restores to normal. The slow acting-relay 100 is slow enough to retract its armatures so th at ground is mamtained on release --trunk'conductor 91 until the-plunger arm of the line switch G" has assumed its positionbefore the trunk line preselected by the-associated master switch G. The ground onrelease'trunk conductor 91 preyentsanother selector switch having access to this trunk line from selecting the line switch G for use until it has assumed its position before an idle trunk line.

In the above manner all-the switohesoperated in the-connectionarcrestored to normal position.

Having fully described and ascertained the features of the invention what is con- SlClEIBCltO-bBIlQW and desired to'haveprotected by Letters Patent willbewpointed-out' in the appended claims.

What I claim as my invention is:

1. In a telephonesystem; a trunk line terminating in a self aligning line switch, trunk lines accessibleto said line switch, means for seizing said; first trunk line and operating said line-switch to seize one of said second trunk lines, meansforcausing" said 11 he switch, when released; to assume a position before another iclle'trunlrline, and means operative while said switchis assume ing-its positionfor applying the busy poten-r tial to said first trunk line.

2. In a telephone system, a trunk line terminating in a self aligning line-switch,

trunk lines accessible to said line switch, means for seizingisaid first trunk line and operating said line switch to seizeone of said second trunk lines, means forcausing said line switch, when released, toassume a positionbeto're'another idle trunk line, and a relay energized while said SWltCh is assuming its position for applying the busy potential to said first trunk line,

3. In a telephone system,selector switches, trunk lines accessible to said selector switches terminating in line switches, trunk lines accessible to said line switches, meansfor operating one of saidiline switches to seize one of said second trunk lines, means for restor: ing said line switchtonormal, and means operating while said switch is being restored to normal for applying busy potential to the associated trunk line. i p

at. In a telephone system,-selector switches,

- then operating the associated'line switch to seize one of said second trun'klines, means for causi-ng'said line switch when released" to assume a position before another idle on e l of sai-d'second trunklines, and means oper- 185 atiVe while said switch; is assuming-its position for applying a busy potential to the associated trunk line in all ofisaid selector switches;

6. In a telephone system, group's-of selector switches, line switches, trunk lines='ac-'- cessible to one group of said'selector'switches--- and terminating-in saidline switches, trunk lines terminating-insaid other group of selectorswitches andaccessible to'said line I switches, means for seizing the selector switches of one groupto cause'the-seizure of the selector switches of the'other group 7 through the medium of certain of "said line switches, means responsive whenall these lectors'of the second group have been seized for making the'line switchesbusytof all selectors of the first'group, means for releasinggf selectors of the second group to cause theirelease of the particular line switchesirused,

and means in said line switches for snaking their associ ated trunks busy" during such re-* lease. a

7. In a telephone system, a seleotorswitch, a lineswitch, meansioperable to cause-said selector to seize said line switch, means re-- sponsive' to such seizure for causing saidline SW1tCh.t0l seize a trunk terminating in a sec 0nd selector switch, means insaid .second' selector for maintainingcsaid first" selector and said'line-switch inan operated position" and to make said line switch busy to'other first selector switches,me ans 'for'releasing said switches, and means operated'whenthe line switch was seized and effective wheirthe release is initiated for maintaining its'associated trunk busy during'its releasing operation. p

8. In a telephone system, a selector switch,

a line switch, means operable to cause said selector to seize said line switch, means're sponsive to such seizure for causing said line switch to seize a trunk'terminatingin'a sec'- ond selector switch, means in sa i'dsecond selector for maintaining said first selector" and said line switch in an operated position and to make said line switch busy to other first selector switches, means for releasing said switches, means operated when the line switch was seized and efiective when the re lease is initiated for maintaining its associated trunk busy during its releasing operation, and means for causing said line switch, when released, to assume a position before an idle trunk line.

9. In a telephone system, trunk lines terminating in line switches, other trunk lines, a master switch for maintaining said switches in position before an idle one of said other trunk lines to which said line switches have access, means associated with said last trunk lines .for maintaining the first trunk lines busy when their respective switches are in an operated position, and means associated with said switches for maintaimng their associated trunks busy during the time required for restoring said switches and for positioning them before the next idle trunk.

10. In a telephone system, trunk lines terminating in line switches, other trunk lines adapted to be seized by said line switches, a master switch for maintaining all idle switches in position before an idle trunk line to which said line switches have access, means associated with said last trunk lines for maintaining the first trunk lines busy while their associated switches are operated, means for releasing said switches, and means associated with said switches for maintaining their associated trunks busy during the time required for their restoratlon to normal.

11. In a telephone system, means including two directive switches for connecting a calling and called line, the connection also including a non-directive switch inserted between said directive switches, means for causing said non-directive switch to select another directive switch when the connection is released, and means for rendering said non-directive switch busy while such selecting operation is taking place.

12. In a telephone system, first selectors, secondary line switches, and second selectors, means for operating a switch of each kind to establish a connection, means for automatically operating the secondary switch in use when the connection is released in order to pre-select a second selector for the nex call, and means for making such secondary switch busy to said first selectors while the pie-selecting operation is taking place.

13. In a telephone system, first selectors, secondary line switches, and second selectors, means for operating a switch of each kind to establish a connection, a master switch for causing the other secondary switches to select an idle second selector when the secondary switch in use is operated, means for causing said last mentioned secondary switch to select the same idle second selector when the connection is released, and means for making such secondary switch busy to said first selectors until its selecting operation is completed.

14. In a plunger line switch, a holding coil for retaining said switch in operated position, a pair of contacts held open while said coil is energized, a slow acting relay connected in circuit with said coil and energized at the same time, a second pair of contacts held closed by said relay when the same is in energized position, and a circuit for making said switch busy including both pairs of contacts in series.

15. In a telephone system, a trunk line including a combined test and holding conductor and terminating in a self aligning line switch, trunk lines accessible to said line switch, means for seizing said first trunk line and for operating said line switch to seize one of said second trunk lines, means for applying a potential to said combined holding and test conductor to hold said line switch operated and to maintain thefirst named trunk line in a busy condition, means for releasing said line switch by removing said potential, means for causing said line switch, when released, to assume a position before another idle trunk line, and means operative while said switch is assuming its new position for applying a busy potential to said combined test and holding conductor to maintain the trunk line busy.

16. In a telephone system, a trunk line including a combined test and holding conductor and terminating in a self aligning line switch, trunk lines accessible to said line switch, means for seizing said first trunk line and for operating said line switch to seize one of said'secon d trunk lines, means for applying a potential to said combined holding and test conductor to hold said line switch operated and to maintain the first named trunk line in a busy condition, means for releasing said line switch by removing said potential, means for causing said line switch, when released, to assume a position before another idle trunk line, a circuit for applying a busy potential to said combined test and holding conductor, and means for closing said circuit responsive to the removal of the busying and holding potential and for again opening it after the switch has assumed its new position.

17. In a telephone system, a trunk line including a combined test and operating conductor and terminating in a self aligning line switch, trunk lines accessible to said line switch, means for seizing said first trunk line and for operating said line switch over said conductor to seize one of said second trunk lines, means for applying a potential to said combined operating and test conductor to maintain the first named trunk line in a busy condition, means for removing said potential and for releasing said line switch,

means for causing said line switch when released to assume a position before another idle trunk line, a circuit for applying a busy potential to said combined test and operating conductor, means for closing said circuit during the release of said switch and for again opening it after the switch has assumed its new position, and means for preventing the application of the busy potential to the combined test and operating conductor during the release of the switch from reoperating the same.

18. In a telephone system, a trunk line including a combined test and operating conductor and terminating in a self aligning line switch, trunk lines accessible to said line switch, means for seizing said first trunk line and for operating said line switch to seize one of said second trunk lines, means for applying a potential to said combined operating and test conductor to maintain the first named trunk line in a busy condition, means for removing said potential and for releasing said line switch, means for causing said line switch when released to assume a position before another idle trunk line, a circuit for applying a busy potential to said combined test and operating conductor, means for closing the busying circuit during the release of the switch and for preventing the application ofthe busy potential to the for applying a potential to said combined operating and test conductor to maintain the first named trunk line in a busy condition, means for removing said potential and for releasing said line switch, means for causing said line switch when released to assume a position before another idle trunk line, a

circuit for applying a busy potential to said combined test and operating conductor, means for closing the busying circuit during the release of the switch and for preventing the application of the busy potential to the combined holding and test conductor at such time from reoperating the switch, and means operative after the switch has assumed its new position for removing the busying potential from said combined holding and test conductor and for preparing the switch for reoperation over such conductor, Signed by me at Chicago, Cook County Illinois, this 1st day of February, 1921.

TALBOT e. MARTIN. 

